In the 1970's, it was discovered that electrical fields could be used to create pores in cells without causing permanent damage to the cell. This discovery made it possible for large molecules, ions, and water to be introduced into a cell's cytoplasm through the cell wall. In some instances, electroporation can be used in topical treatments, such as for head and neck cancer, to introduce chemicals and other compounds into the tumor. During these procedures, the patient may not be under general anesthesia so pain and involuntary muscle movement should preferably be minimized.
Some electroporation devices can produce pulse trains that induce electroporation within a cell's wall to allow the introduction of large molecules, ions, and water into the cell's cytoplasm. However, their electric field or signal frequency (generally about 3.3 Hz) necessary to create the electroporation effect might cause the patient to experience significant pain while receiving treatment. The pain may be at least in part a result of an inverse effect that the frequency or electric field has on skin impedance when an electromagnetic wave is traveling through flesh. For example, skin impedance at 50 Hz is approximately 32000Ω while skin impedance at 4000 Hz is reduced to approximately 40Ω. It has been observed that the higher the impedance, the greater the pain.
Therefore, there is a need in the art for an electoporation device that delivers a strong enough pulse for delivering an agent for treatment, but prevents pain due to cell structure impedance.